Aircraft propeller drive



Dec. 5, 1950 J. J. BLOOMFIELD AIRCRAFT PROPELLER DRIVE 4 Sheets-Sheet 1Filed Feb. 21, 1946 ELD lNVE JOHN J. BLOO Agent,

1950 J. J. BLooMHELb 2,532,755

AIRCRAFT PROPELLER DRIVE Filed Feb. 21, 1946 4 Sheets-Sheet 2 INVENTOIL,JOHN' J. BLOOMFIELD Dec. 5, 1950 J. J. BLOOMFIELD AIRCRAFT PROPELLERDRIVE Filed Feb. 21, 1946 4 Sheets-Sheet s 4 .z .& IOO

M. M. 4 M: A

36 3s A u g INVENTOR.

JOHN J. BLOOMFIELD Dec. 5, 1950 J. J. BLOOMFlELD 2,532,755

AIRCRAFT PROPELLER DRIVE Filed Feb. 21, 1946 4 Sheets-Sheet 4 .ZVIIIIILINVENTOR. JOHN J BLOOMFIELD' 2' Agent.

Patented Dec. 5, 1950 i AIRCRAFT PROPELLER DRIVE John J. Bloomfield,Burbank, Calif., assignor to Lockheed Aircraft Corporation, Burbank,Calif.

Application February 21, 1946, Serial No. 649,339

8 Claims.

This invention relates to power transmittin equipment, and relates moreparticularly to propeller drives for aircraft. It is a general object ofthe invention to provide a practical, effective selected resistance sothat the shaft may find its own axis of rotation to reduce vibration andto reduce the transference of vibration to the fuselage and structure ofthe airplane. End or axial propeller drive which reduces vibrationeffects to 5 thrust is dependably transmitted from the shaft a minimum.to the structure, while at the same time vibra- In aircraft employingpropellers as a means of tion and whipping is reduced to a large degreepropulsion, it is desirable to reduce the transmisby the friction-allyresisted ability of the shaft to sion of propeller vibration to theaircraft struc find its own axis of rotation. ture. In situations wherethe propeller is remote 10 A. still further object of the invention isto profrom the engine and a long shaft is employed, vide a propellerdrive in which the several above there is a tendency for the shaft tovibrate and mentioned features and elements mutually conaggravate thevibration of the propeller. In an tribute in reducing propeller andpropeller shaft airplane having the engine well forward in thevibration, and in avoiding the transmission of fuselage and a pusherpropeller aft of the emsuch vibration to the airplane structure.pennage, it is desirable to isolate, as far as pos- Other ob ects andfeatures of the invention sible, the vibration of both the propeller andwill be readily understood from the following deshaft from the fuselageand other parts of the tailed description of typical preferred forms ofairplane structure. In the following description the invention whereinreference will be made to I will describe the invention embodied in anairthe accompanying drawings in which: plane of the general class justmentioned, it be- Figure 1 is a side elevation of an airplane ingunderstood that this is merely a typical appliembodying one form ofdrive of the invention cation and embodiment of the invention. with aportion broken away to show the drive in It is an important objective ofthe invention to elevation; provide a propeller drive for use in anairplane Figure 2 is an enlarged end view of one of having a long, orrelatively long, shaft extending the flexible couplings being a viewtaken subfrom the engine to the propeller which embodies stantially asindicated by line 2-2 on Figure 1; means for reducing vibration of theshaft and Figure 3 is a fragmentary longitudinal section propeller n fisolating r i ciating the taken substantially as indicated by line 3-4on residual vibration from the airplane structure. so Figure 2;

Another object of the invention is to provide Figure 4 is an enlargedfragmentary sectional a p op l drive h vin means f r mpin r view of thecouplingtaken as indicated by line reducing propeller vibration at thepropeller hub 5-4 on Figure 2; and for eliminating to a substantialdegree, the Figure 5 is a side elevation of one of the transmission ofpropeller vibration to the shaft. 3:, spring links of the coupling;

The improved drive of the invention embodies a Figure 6 is an enlargedlongitudinal section of sleeve assembly of resilient vibration absorbingthe flexible coupling at the engine shaft, illusmaterial interposedbetween the propeller and its trating the centralizing means;

Shaft, Which materially damp n p p er vibra- Figure '7 is an enlargedlongitudinal section tion and isolates the vibration from the propeller40 illustrating the propeller hub and thrust bearshaft. ing assembly;

Another object of the invention is to provide a Figure 8 is an enlargedfragmentary sectional propeller drive incorporating improved flexibleview of a portion of the propeller hub mountc plin interposed at one ormore points in the ing of slightly different construction; propellershaft for absorbing angular and tor- Figure 9 is a fragmentary sideelevation of sional vibration, and for reducing the transmisan airplaneembodying another form of prosion of n ne vibra ion o he sh f Theimpeller drive of the invention with the airplane proved couplings areflexible axially of the shaft, broken away to show the drive in sideelevation; an a y in all ons with respect to the Figure 10 is anenlarged front elevation of shaft, and are torsionally flexible, yetstrong and 5 the intermediate shaft bearing taken substanlight inWeight/- tially as indicated by line ill-l0 on Figure 11;

A further object of the invention is to provide and,

a propeller drive of the class referred to embody- Figure 11 is avertical sectional view of the i n l bearing means for the Shaft Which Dintermediate bearing taken substantially as indimit limited radialmovement thereof against a cated by line l|-Il on Figure 10.

In the drawings, the invention is illustrated incorporated in anairplane in which the propeller P is spaced aft of the empennage, andthe engine E is well forward in the fuselage. The invention is, ofcourse, adapted for use in aircraft of other designs and is not to beconstrued as restricted to the particular installation or details hereindescribed. The portion of the airplane appearing in Figures 1 and 8comprises a fuselage it provided at its aft end with an empennage i i,and at its under side with apprbpriate landing gear 52. The engine E ismounted in the fuselage it! behind the pilots compartment i3 and iscooled by a fan [4- associated with its shaft. Suitable mounting meansi5 supports the engine E. A substantially vertical bulkhead I6 isprovided in the fuselage it just forward of the empennage i. Thepropeller P is at the rear of the empennage i I and. is arranged to haveits axis in alignment with the axis of the engine. which is inclinedupwardly and rearwardly, assuming the airplane to be in the attitude ofFigures l and 9.

The embodiment of the invention shown in Figures 1 to 8 inclusive, and10 and 11, may be said to comprise generally a shaft S, flexiblecouplings I? associated with the shaft, means A8 for securing thepropeller P to the shaft, and bearing means it! and 9 for the shaft.

The shaft S serves to transmit power from the engine E to the propellerP and extends real wardly through the fuselage I 0 to project beyond theempennage H. In accordance with the invention, the shaft S is tubular toreduce its weight and inertia, and in practice, may be formed of one ormore lengths of Dural tubing, or tubing of other suitable light-weightalloys. It is contemplated that the shaft S may be a single, continuous,one-piece member extending from the engine shaft to the propeller hubassembly. However, where the mounting of the engine E permits limitedmovement or vibration of the engine in a lateral direction, it may bedesirable to employ a shaft having at least two sections connected by aflexible coupling ll. In Figure 1 it will be assumed that the enginemounting means i5 allows lateral vibration, and I have shown a shaft Scomprising two sections as and 2! connected by a coupling IT. A similaror identical coupling i! connects the shaft [5 with the engine shaftI09.

The two couplings ll may be identical, and I' will proceed with adetailed description of the couplmg which connects the two shaftsections 22 and 2!, it being understood that this description isapplicable to the other coupling, and that corresponding referencenumerals are applied to corresponding parts of the two couplings.

The coupling is constructed to be flexible or somewhat yieldable axiallyof the shaft as well as in all directions angularly of the shaft it andto have torsional resiliency. The coupling includes two similar flangemembers 22 fixed to the adjacent opposing ends of the shaft sections 2i)and 2 i. As best illustrated in Figures 2 and 3, the members 22 aresubstantially triangular in outline, each having three radiallyprojecting apex parts or ears 23, and each having a hub 2 for attachmentto the respective shaft section. The tubular hubs 24 are of sufficientlength to have extensive connection with the shaft sections. Theinvention contemplates that the hubs may be either secured within thetubular shaft sections, or secured to the exteriors of the shaft parts.In either case it is preferred that the connection be effected by asynthetic cement layer. In the drawings I have shown the hubs 24 engagedaround the shaft sections 20 and 2!, and shrunk thereon to be secured tothe shafting by intermediate layers of a suitable cement such asCycleweld. The shrinking operation assures the effective bonding contactof the cement to the shaft sections and hubs throughout the entireextents of the hubs. It is to be understood that in operation of thedrive, the stress is actually transmitted by the cement and not bydirect metalto-metal contact. Where the hubs 24 are secured around theshaft sections 20 and 2!, it may be desirable to provide reinforcingsleeves 26 within the shafting.

The two coupling members 22 are related so that their ears 23 areangularly offset, the ears of one member being offset substantially 60from the adjacent ears of the other member. Axial openings 21 in theears 23 receive bolts 28, and nuts 29 are provided on the bolts tocooperate with the outer sides of the ears. There is a separate bolt 28associated with each ear 23. It is preferred to equip the bolts 28 withlock nuts, or with nuts that will not work loose.

A tubular spacer 30 is engaged on each bolt 28 to seat in a counterborein the inner side of the adjacent ear 23.

Angularly and axially flexible and torsionally resilient link assembliesextend between the adjacent bolts 28 of the two flange members 22 forthe transmission of torque or driving loads between the two shaftsections 20 and 21. Each of these link assemblies comprises two groupsof hardened spring steel links or leaves 3!. The leaves 3| may have athickness of approximately .006 inch, and are preferably hardened toabout 300,000 pounds ultimate strength. Each group of link leaves 3|comprises a plurality of similar leaves engaged in face-to-face relationto form a compact assembly of high strength of considerable resiliency.The two groups of leaves 3! of each link assembly are provided at theiropposite ends with openings 32 for receiving the bols 28. The links orleaves 3| are preferably shaped to each have two end lobes havingperipheries concentric with their openings 32, the lobes being joined bynarrow ties or necks having a width substantially equal to the effectivewidth of the perforated lobes. This is shown in Figure 5. As illustratedin Figure 4, the lobe portions of adjacent link assemblies areoverlapped at the bolts 28 and their end portions are clamped togetherbetween the above mentioned spacers 30 and the heads of the bolts.

Each link assembly further includes a core or spacer 33 of resilientmaterial engaged between its two bundles of spring leaves. 1 e bundlesor groups of leaves 3! are bowed outwardly or away from one another, andthe resilient spacers 33 are received between and shaped to conformgenerally to the bowed portions of the leaves. The spacers 33 are formedof rubber, synthetic rubber or similar elastic material which compressesor flows when the transmission of torque through the related linkassemblies tends to straighten the bowed leaves 3! and which expands ortends to return to its original configuration when the torque load isremoved from the links. The spacers 33 are tightly engaged between thesets of link leaves 3|, but it is desirable to provide means forpreventing radial displacement of the spacers by centrifugal force.

' This means may consist of flanges 34' on the spacers 33 for engagingthe inner and outer edges of the link leaves 3| to hold the spacersagainst outward movement.

The flexible resilient sets of link leaves 3i allow limited axial andangular relative movement between the shaft sections 29 and 2|, and theresilient spacers 33 provide for torsional resiliency and flexibility inthe coupling. It will be observed that there are six link assemblies inthe particular coupling illustrated. Three of these link assembliestransmit torque or load in one direction, and the three intervening oralternate link assemblies transmit torque applied in the otherdirection. Upon an increase in the torque load in one direction, threespaced link assemblies are subjected'to increased tension so that theirbowed spring leaves 3| tend to straighten out. The resultant inwardfiexure of the spring steel leaves 3| is yieldingly resisted by theresilient spacers 33. This imparts torsional resiliency or flexibilityto the link assemblies and the shaft coupling. This torsional resiliencyand flexibility, combined with the angular flexibility inherent in thelink leaves 3|, gives the assembly substantially universal flexibility.

It is desirable to provide centralizing means in the flexible couplingsll to maintain the connected shaft sections in coaxial relation and toprevent disassociation of the sections in the event of failure of thecouplings. The centralizing means may be incorporated in both couplingsll, although I have omitted this feature from Figures 2, 3 and 4 for thesake of clarity. Referring now to Figure 6, which illustrates thecoupling ll between the engine shaft l8?) and the shaft S, thecentralizing means includes a tube member ill} threaded on the endportion of the engine shaft its. A safety wired pin iii locks the memberI i ii on the shaft and the meinber is shouldered at its forward end tocooperate with a bushing of the hub assembly M2 for the fan Id. Themember He extends rearwardly to enter a flanged tubular element H3secured in the coupling member 23. The element H3 surrounds the tubularmember H!) with considerable clearance. The centralizing means furtherincludes a ring id of Micarta, or the like, fixed on the exterior of themember llll as by Cycleweld cement. It is preferred to spherically curvethe periphery of the ring I I4 about a point at the intersection of thelongitudinalaxis of the shaft assembly and the central transverse planeof the coupling M. This permits a universal joint action at the couplingH.

The propeller hub means I8 provides for the dependable connection of thepropeller P with the shaft assembly without the necessity of employingpropeller-engaging bolts, or the like, and without the danger ofsplitting the propeller hub. It is a feature that the improved hub meansof the invention is effective in absorbing or dampening propellervibration and shaft vibration. The propeller mounting means includes atubular member 35 secured to the aft end of the shaft S to constitute anextension thereof. The member 36 may be secured to the shaft in anyappropriate manner, but it is preferred to employ a cemented connectionof the type illustrated. The member 36'is enlarged in external diameterat its forward end and this enlarged portion is entered in the rear endof the shaft section 2|. A layer of synthetic cement such as Cycls'weldis provided between surfaces of the shaft section 2| and the member 36,and the shaft section is shrunk onto the member to assure a uniform andcontinuous 6 cement bond. It will be apparent that if desired thearrangement just described may be reversed, in which case the member 36is cemented and shrunk onto the exterior of the shaft section 2|.

The shaft extension member 36 continues rearwardly from the shaft andpasses through a central opening 37 in the propeller hub. The externaldiameter of the member 33 is considerably less than the diameter of thepropeller opening 31, and the member is of sufficient length to extendrearwardly beyond the propeller hub. A body of flexible resilientmaterial such as rubber, rubber composition, or synthetic rubber,occupies the annular space between the wall of the opening 37 and theperipheral surface of the member 36. This body of material may beprovided in the form of a single tubular part, but I prefer to employ aplurality of separately formed rings 38 of the flexible resilientmaterial which surround the member 36 and engage the wall of thepropeller opening 31. End rings 39 constructed of the same or a similarelastic material surround the member 33 at the ends of the series ofrings 38. The end rings 39 are larger in external diameter to haveportions projecting radially outward at the ends of the propeller hub.

The rings 38 and 39 are maintained under compression to provide a torquetransmitting connection between the shaft extension member 36 and thepropeller P. The means for applying and maintaining the compression onthe rings 38 and 39 includues a metal ring 33 engaged by the forward endring 39 and a metal ring 4| engaging the rear end ring 39. The forwardring 43 is flanged or increased in external diameter to cooperate withan extensive area of the forward rubber ring 39, and its rear faceslopes forward and radially outward. The compression ring 4|] is heldagainst forward displacement by an element of the thrust bearing meansto be subsequently described. The rear compression ring 4| has aradially and rearwardly sloping surface for engaging the rear rubberring 39. A tubular stub or stud I20 is arranged in the shaft extension35 to engage rearwardly against a shoulder |2| in the extension. Thestud |2il projects rearwardly from the washer or ring 4| and a nut 43 isthreaded on the projecting portion to clamp against the ring. A dowelpin I22 holds the ring against rotation. The parts are proportioned andrelated so that when the nut 53 is tightened down to bring the ring 4!to its final position, the rings 38 and 33 are compressed to the extentthat they form a positive, dependable, yet somewhat yielding, connectionbetween the propeller P and the member 36. During tightening down of thenut 43, the rubber rings 38 and 39 are compressed in the axial directionand expand radially inward and radially outward; that is, the materialof the rings flows radially in both directions. This brings the materialof the rings 38 and 39 into tight frictional cooperation with the wallsof the propeller hub opening 3'! and the propeller surface of the member36, and compacts the material so that it forms a strong loadtransmitting annular layer between the shaft extension member 36 and thepropeller P. The material of the compressed rings 38 and 39 actssomewhat in the manner of a fluid, and the expansive forces or radicalpressures which it exerts on the propeller P and the member 33 areuniformly distributed. The torque loading, during operation, is likewiseuniformly distributed throughout the engaged surfaces of the member 33and propeller P.

There may be a tendency for the material of the end rings 39 to flow orextrude from between the hub surfaces and the compressing rings and M. Ametal band 4 engages around the periphery of each ring 39 and rings ofcurved or substantially L-shap'ed cross section are arranged to engagethe side faces of the rings 39 and to lap over the bands 34. The innerflanges of the rings 45 engage the end surfaces of the compressing ringsas and d! and the ends of the propeller hub. The bands 44 and rings 45define the peripheral parts of the 'endmost rubber rings 39 to preventradial extrusion of the rubber or rubber-like material. The propellermounting just described is effective in securing propellers of anyconstruction to their drive shafts, but is particularly advantageous inmounting wooden propellers because it avoids the necessity of engagingthe propeller with metal bolts, clamps, and the like, and there is noneed to weaken the propeller hub by the provision of bolt holes. It willbe noted that the compressed radial flanges of the endmost rubber rings39 center the propeller P and hold it against axial movement.

Figure 8 illustrates a modification of the propeller mounting whichprovides for increased torsional or angular flexibility. In thisconstruction, the member 35, the inner elastic rings 38, and thecompressing plates 45% and 4!, may be substantially the same asdescribed above. However, the compression plate 6% is actuated andsecured b screws 53 threaded into openings in the end of the shaftextension Instead of the one-piece end rings 39, sectional or laminatedring assemblies are provided at each end of the propeller hub. Each ofthese assemblies comprises a plurality of rings or discs 4'? of selectedelastic material arranged in face-to-face relation between the rings 4and ti, and the ends of the propeller. Th discs together with rings 38,are subjected to compression when the screws are tightened down. Thediscs 4'! are provided with rims ltd of metal which are generally LI-shaped in cross section to engage over the peripheries of theirrespective discs ll and to have side flanges engaging the side faces ofthe discs. These side flanges are of substantial extent, and the flangesof the rims on the adjacent discs 4'! bear one against the other. Thisarrangement is such that there may be limited angular movement betweenadjacent discs 4'! when the assembly is subjected to varying torqueloading, the relative movement absorbing or dampening out the vibrationthat otherwise might result. The individual discs 4? and their rimsprovide a substantial number of cooperating surfaces where the desirablelimited relative movement may take place and thus impart considerabletorsional resiliency to the propeller mounting.

In an airplane of the general type illustrated, where the propeller P ispositioned at the rear of the empennage, the problem of mounting thebearings for the extended shaft S is encountered. The present inventionprovides a thrust bearing means located adjacent the propeller hub andsupported from the above mentioned bulkhead 16 of the airframestructure. A bearing supporting tube s5 is fixed to the bulkhead it andextends rearwardly therefrom in spaced surrounding relation to the shaftsection 2 i. The tube 45 passes freely through the empennage structureand projects rearwardly beyond the empennage to have its rear portionsurround the forward part of the shaft extension member 36. The improved8 thrust bearing assembly of the invention mounts the member 36 in theaft end of the tube 46. The tube 46 is a rigid member capable ofadequately supporting the thrust bearing independently of the adjacentempennage structure.

The thrust bearing assembly includes an inner race 48 engaged on theshaft member 35, an outer race 49 and a series of balls 50 engagedbetween the races. The inner race 48 seats against a rearwardly facingshoulder 41' on the member 36 through the medium of a flanged sleeve Hi!and forms a stop or abutment for preventing forward movement of theabove described ring 40 of the propeller mounting means. A ring 53surrounds the outer race 49 and annular plates 5| engage the front andrear faces of the race 49 to substantially close the annularball-carrying space between the two races. Circumferentially spacedbolts 54 pass through axial openings in the plates 5| and the ring 53 tosecure the plates in position. The parallel plates 51 extend radiallyoutward beyond the ring 53.

The thrust bearing means further includes an assembly on the abovedescribed tube 41. This assembly includes an annular channel-shaped orflanged member '55 suitably secured to the interior of the tube ii. Aring 56 is attached to the member 55 by spaced bolts '51 to be in spacedsurrounding relation to the ring 53 of the inner assembly. A centralannular flange 58 projects inwardly from the ring 56 toward the innerring 53. The opposing surfaces of the ring 53 and flange 58 are inspaced concentric relation. The above described plates 5i lap over theflange 58 with clearance.

The floating thrust bearing means further includes means for yieldinglyresisting lateral or radial play of the shaft assembly and for dampeningor absorbing vibration. This means comprises rings of elastic materialsuch as rubber, rubber composition, or the like, clamped between theplates 5| and the sides of the flange 58. The outer peripheries of therings 65 engage the internal surface of the ring 56 and the internalsurfaces of the yielding rings have engagement with the inner ring 53.The thrust bearing means just described serves to transmit the endthrusts from the shaft assembly to the rigid tube 47, which in turn,carries them directly to the fuselage structure. The yielding rings 55engaged between the thrust plates 5| and the flange 513 permit limitedlateral and axial movement of the shaft assembly, which movement iscontrolled or resisted by the confined elastic material of the rings.The yielding rings 65 effectively isolate shaft and propeller vibrationfrom the airframe and allow the shaft to find its own center of rotationwithin defined limits.

The bearing means 9 is provided t the bulkhead IE or similar part of theairplane structure to support the shaft S at a point intermediate itsends. The character of the bearing means 9 depends to some extent uponthe manner in which the engine E is mounted, and upon the flexibility ofthe propeller drive as a whole. I have shown a midship bearing for theshaft S which may be set or adjusted to provide for any selectedresistance to radial or lateral movement of the shaft. With a propersetting or adjustment, the bearing means allows the shaft S to find itsown axis of rotation but offers desirable frictional resistance tovibration and lateral motion. The construction is such that iteffectively isolates vibration of the shaft from the airframe and yetprovides ample bearing support for the intermediate portion of theshaft.

Referring to Figures 10 and 11, it will be seen that the bulkhead I6 hasan opening 68 pass- 'ing the shaft S with substantial clearance. A

mounting adaptor 69 is fixed to the front face of the inclined bulkheadto, surround the opening 68 and present a forward face 10 which issubstantially normal to the longitudinal axis of the shaft S. The face lis annular, and a gasket ring I! of frictional material is cemented to.it. A steel bearing carrier or ring 12 is arranged to bear against thefriction ring 1 I, being held in position by bolts 13 engaged inopenings in the adapter 69. Link-like retainers 14 are engaged onadjacent pairs of bolts 13 to bear against the forward face of the ring12. The nuts 15 threaded on the bolts 13 urge the retainers M againstthe ring 12 and accordingly urge the ring against the friction material10. Friction material shoes 16 may be provided on the inner faces of theretainers M to cooperate with the ring 12. The -retainers 14 may be inthe form of leaf springs to exert controlled pressure against the ring12 as determined by the setting of the nuts 15. In any case, the nuts 15may be adjusted or set to provide any selected resistance to movement ofthe plate or ring 12 relative to the adapter 69. The openings 90 in thering 12 which pass the bolts 13 are enlarged in diameter with respect tothe bolts to allow limited controlled or resisted movement of thecarrier ring relative to the adapter 69.

The bearing means 9 further includes spaced anti-friction rollersmounted on the carrier or ring E2 to support the shaft S. Where theshaft S is constructed of an aluminum alloy, or the like, it ispreferred to provide a wear resistant band 80 of steel on the shaft tobe engaged by the rollers. The wear-taking band 80 may be cemented tothe shaft. There are preferably three spaced shaft supporting rollers,two side rollers 8| and a lower roller 82. The rollers 81 and 82 arecarried by anti-friction bearings 83 which in turn are mounted onbushings 84 supported by studs 16. The studs 16 project forwardly frombrackets Tl welded or otherwise fixed to the ring 12. The bushing 84 ofthe lower roller assembly is constructed to permit adjustment of theroller 82. An eccentric longitudinal opening in this bushing 84 receivesthe mounting stud 76 whereby the roller may be adjusted with respect tothe shaft S. Upon tightening of the nut Slon the stud T6 the bushing 86is set or secured in the adjusted position. The upper or side rollers 8icooperate with the shaft band 89 at points well above the centralhorizontal plane of the shaft while the lower roller 82 engages the bandat a central lower point. With this three-point roller contact, theshaft S is constrained against lateral or radial movement relative tothe carrier ring 12, or in other words, the ring is obliged to move withthe shaft in lateral directions. Such movement of the carrier ring 12 isresisted by the friction shoes 16 and friction gasket H3, and isdefinitely limited by the engagement of the walls of the openings 98with the bolts l3.

Figure 9 illustrates an embodiment of the invention having a continuousor one-piece shaft 95. A one-piece shaft of this kind may be em ployedwhere the engine mount i is such that vibration of the engine iscontrolled or kept at a minimum. A flexible coupling l! serves toconnect the shaft 95 with the crankshaft of the en gine Fhe coupling ll,propeller hub assembly t8, the thrust bearing l9 and the midship bearing10 9 are the same as described above and corresponding referencenumerals are applied to corresponding parts in the two illustrated formsof the invention.

From the above detailed description it will be seen that I have provideda dependable lightweight propeller drive useful where an extended orelongate drive shaft is required. The flexible coupling means E1, thepropeller mounting l8 and the two bearing means l9 and 9 mutuallycooperate in reducing shaft vibration to a minimum and in isolating thevibration from the airframe structure. The flexible coupling means I!allows fiexure in the direction of rotation of the shaft, axially of theshaft, and in all directions angular of the shaft, and yet is positivein the transmission of torque. The resilient rings 38 and 39 of thepropeller hub assembly assist in dampening vibration and effectivelytransmit torque by friction from the shaft means to the propeller. Thevibration absorbing thrust bearing means if! transmits the end loadsfrom the shaft assembly to the airframe structure through the medium ofthe tube 41, and allows the shaft assembly to find its own axis ofrotation. This latter feature eliminates the transmission ofconsiderable propeller and shaft vibration to the airplane. The midshipbearing means 9 dependably supports the intermediate portion of theshaft, while offering yielding or frictional resistance to radial orlateral movement. In this way the shaft may find its own axis ofrotation Within a limited range of movement, but whipping of the shaftis effectively controlled. In initially installing the mechanism, theshaft may be accurately aligned and centered before tightening the nuts,and subsequently, resistance to shaft vibration may be readily regulatedby adjusting the nuts 15. The bearing means 9 is simple in constructionand its parts are readily accessible for inspection and replacement.

Having described only typical forms'of the invention, I do not wish tobe limited to the specific details herein set forth, but wish to reserveto myself any variations or modifications that may appear to thoseskilled in the art or fall within the scope of the following claims.

I claim:

1. In an airplane having a fuselage and an empennage the combination of,an engine mounted in the fuselage, a propeller spaced to the rear of theempennage, a drive shaft coupled with the engine and extending to thepropeller to drive the same, a tubular member spaced around the shaftand having its forward portion in the fuselage, the member passingfreely through the empennage to adjacent the propeller, means fixedlysecuring the forward portion of said member in the fuselage so that themember constitutes a canti lever, and thrust bearing means for the shaftcarried by the rear portion of the member.

2. In an airplane having a fuselage and empennage the combination of, anengine mounted in the fuselage, a propeller spaced to the rear of theempennage, a drive shaft coupled with the engine and extending. to thepropeller to drive the same, a support in the fuselage between the endsof the shaft, bearing means carrying the intermediate portion of theshaft, means mounting the bearing means on the support for limitedresisted movement in a .plane substantially normal to the longitudinalaxis of the shaft so that the shaft may find its axis of rotation, andthrust bearing means for the aft end portion of the shaft.

3. In an airplane having a fuselage and an empennage the combination of,an engine mounted in the fuselage, a propeller spaced to the rear of theempennage, a drive shaft coupled with the engine and extending to thepropeller to drive the same, a support in the fuselage between the endsof the shaft, bearing means carrying the intermediate portion of theshaft, means mounting the bearing means on the support for limitedresisted movement in a plane substantially normal to the longitudinalaxis of the shaft so that the shaft may find its axis of rotation, athrust bearing for the aft end portion of the shaft, and meanssupporting the thrust bearing for limited floating movement.

4. In an airplane having a fuselage and an empennage the combination of,an engine mounted in the fuselage, a propeller spaced to the rear of theempennage, a drive shaft coupled with the engine and extending to thepropeller to drive the same, a support in the fuselage between the endsof the shaft, bearing means carrying the intermediate portion of theshaft, means mounting the bearing means on the support for limitedresisted movement in a plane substantially normal to the longitudinalaxis of the shaft so that the shaft may find its axis of rotation, meansfor regulating the resistance to movement of the bearing means, andthrust bearing means for the aft end portion of the shaft.

empennage the combination of, an engine mounted in the fuselage, apropeller spaced to the rear of the empennage, a drive shaft coupledwith the engine and extending to the propeller to drive the same, asupport in the fuselage between the ends of the shaft, an adapter on thesupport presenting a surface normal to the shaft, a carrier arranged forlimited movement on said surface, bearing means on the carrier forsupporting the intermediate portion of the shaft, and means forfrictionally resisting movement of the carrier on said surface.

6. In an airplane having a fuselage and an empennage the combination of,an engine mounted in the fuselage, a propeller spaced to the rear of theempennage, a drive shaft coupled with the engine and extending to thepropeller to drive the same, a support in the fuselage between the endsof the shaft, an adapter on the support presenting a surface normal tothe shaft, a carrier arranged for limited movement on said suri2 face,bearing'means on the carrier for supporting the intermediate portion ofthe shaft, and means for frictionally resisting movement of the carrieron said surface, and means for urging the carrier toward said surface.

7. In an airplane having a fuselage and an empennage the combination, anengine mounted in the fuselage, a propeller spaced to the rear of theempennage, a drive shaft coupled with the engine and extending to thepropeller to drive the same, a support in the fuselage between the endsof the shaft, an adapter on the support presenting a surface normal tothe shaft, a carrier arranged for limited movement on said surface,bearing means on the carrier for supporting the intermediate portion ofthe shaft, friction means for resisting movement of the carrier on saidsurface, and means for regulating the frictional resistance to suchmovement.

8. In an airplane having a fuselage and an empennage the combination of,an engine mounted in the fuselage, a propeller spaced to the rear of theempennage, a cooling fan driven by the engine shaft at the rear thereoffor circulating air rearwardly over the engine, a propeller shaftextending rearwardly through the empennage to the propeller to drive thesame, a flexible coupling between the engine shaft and propeller shaft,bearing means for the shaft, and means mount- H; ing the bearing meansfor limited resisted lateral 5. In an airplane having a fuselage and anmovement.

JOHN J. BLOOMFIELD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,180,347 Warren Apr. 25, 19161,386,493 Guyot Aug. 2, 19 1 1,414,241 Wells Apr. 25, 1922 1,763,409Orsett June 10, 1930 1,947,052 Lock Feb. 13, 1934 2,305,454 NallingerDec. 15, 1942 2,326,104 Petrich Aug. 3, 1943 2,367,190 Badrutt Jan, 16,1945 OTHER REFERENCES Publications: Aviation, page 47, April 1941; ibid,pp. 37-41, Feb. 1947; and Janes All the Worlds Aircraft, page 2230,1947.

